The invention relates to an apparatus for infusion of medicaments, in particular heparin, into the partial vacuum region of an extracorporeal blood circuit, in particular an extracorporeal blood circuit of a dialysis apparatus, comprising a supply container for the medicaments and a feed conduit from the supply container to the extracorporeal blood circuit.
The operation of an extracorporeal blood circuit involves the necessity of inhibiting by addition of suitable medicaments the blood coagulation initiated by contact with the surfaces of the extracorporeal blood circuit. The medicament most frequently used for this purpose is heparin. As a rule, infusion into the blood circuit is carried out continuously and for this purpose either syringe pumps or peristaltic pumps are used. In exceptional cases, if there is a particular danger of hemorrhage, in a dialysis apparatus the effect of the heparin is cancelled again downstream of the blood purifying apparatus by adding another substance, for example prothrombin.
DE-A 2,851,064 admittedly discloses a dosing device for a hemodialysis apparatus which has a water supply valve and separate means, preferably in the form of floats, as known per se but this device is not used to infuse medicaments into the partial vacuum region of an extracorporeal blood circuit because the known device serves to feed dialysate solution previously prepared in special containers into a hemodialysis apparatus. In addition, the aforementioned water supply valve is not arranged in the supply conduit to the extracorporeal circuit but in a water supply conduit lying between a water source and the mixing containers. Finally, since neither a pressure measuring means in the extracorporeal blood circuit nor a control means connected thereto is described this dosing device known from DE-A 2,851,064 is not an apparatus comparable to the apparatus according to the invention.
Finally, DE-A 2,644,062 describes an apparatus for automatic regulation of a hemodialysis apparatus which however teaches the use of pressure measurement only for regulating the speed of a blood pump.
The extensive use of extracorporeal circuits in particular in the field of hemodialysis has led to a large cost burden, in particular on insurance systems, and this in turn has led to a corresponding pressure on the prices of apparatuses and disposable articles. It is therefore the objective of numerous developments to configure the apparatuses constructionally so that without restricting the medical treatment quality or with an improved treatment quality the costs are reduced by reduced material costs and also simpler operation.
The problem underlying the present invention is therefore to provide an apparatus with which it is possible to infuse medicaments into an extracorporeal blood circuit and which for the same treatment quality has a simpler construction than the known apparatuses and is thus more economical to produce.
This problem is solved in an apparatus of the type mentioned at the beginning by the characterizing features of claim 1.
Instead of the heparin pump used hitherto for pumping the corresponding medicament in accordance with a previously defined rate from the supply container into the extracorporeal blood circuit in accordance with the invention said supply container is merely connected to the partial vacuum section of the extracorporeal circuit via a shutoff member which may be a clamp. To actuate said shutoff member, a control means is provided which in dependence upon the partial vacuum obtaining in the extracorporeal blood circuit and the desired medicament rate periodically opens and closes the shutoff member. For measuring the reduced pressure a corresponding measuring means is provided which is arranged downstream of the connection point of the supply or feed conduit in the extracorporeal blood circuit. The control means is connected to said manometer or pressure measuring means. Since in most cases a corresponding pressure measuring device is already present in the extracorporeal blood circuit it is merely necessary to provide an additional connection of this pressure measuring means to the control unit.
The control means is notified of the desired drug or medicament infusion rate via an input device, not shown. Preferably, in the feed conduit either between the medicament supply container and the shutoff member or between the shutoff member and the connection point of the feed conduit to the extracorporeal blood circuit a flow throttle is also incorporated which has a flow resistance which is fixed to take account of the respective medicament viscosity. The control means then controls the clamp in dependence upon the given infusion rate and the partial vacuum measured in such a manner that via the throttle exactly the set amount of medicament flows into the extracorporeal system, the control means being constructed in such a manner that the flow resistance of the throttle or constriction is taken into account.
The apparatus according to the invention can be used in all extracorporeal circuits provided that a partial vacuum obtains in the flexible tube section to which the feed conduit is connected.
In a dialysis apparatus the apparatus according to the invention is arranged in the arterial line of the extracorporeal blood circuit between the patient and blood pump. By the blood pump the necessary partial vacuum is generated which on opening of the shutoff member in the feed conduit leading to the medicament container effects that the medicament solution is aspired from the supply container. By corresponding opening and closing of the shutoff member by means of the control means in this manner the desired amount of medicament is supplied to the extracorporeal blood circuit without an additional pump being necessary as was the case in the prior art.
In extracorporeal circuits operating with a single-needle technique the shutoff member is opened only during the arterial aspiration phase. The control means is constructed in accordance with this purpose.
If the extracorporeal circuit is to be connected via an arterial-venous shunt effecting a positive pressure in the extracorporeal circuit upstream of the pump then by interconnection of a constriction or throttle into the arterial aspiration conduit the necessary partial vacuum can be produced upstream of the blood pump.